1. Field of the Invention
This invention relates to a compound bow, and more particularly to a compound bow that is operable to provide a plurality of adjustments in the draw length and/or a draw weight for eccentric pulleys of a given size on the limbs of the bow.
2. Description of the Prior Art
Compound bows, as well known in the art, utilize eccentrically positioned arrow string or cable mounting devices secured to the free ends of the bow limbs. The arrow string portion of the cable is reeved around the eccentric devices which includes wheels, pulleys and the like and are operable to provide a mechanical advantage to increase the amount of potential energy stored in the limbs as the arrow string is drawn. With this arrangement, when the arrow string is in the full draw position maximum potential energy is stored in the bow where the force required to maintain the arrow in the full draw position is less than the maximum draw weight of the bow. As the arrow string portion is being drawn, the draw weight or force applied to the bow increases to a maximum draw weight and lets off to a lower draw weight at the full draw position. Maximum energy is stored in the limbs without requiring maximum force to be applied to the arrow string to hold the arrow string at the full draw position. This substantially improves the performance of the bow and the ease of operation thereof. Samples of compound bows utilizing eccentric pulleys are disclosed in the following U.S. Pat. Nos.: 3,486,495; 3,948,551; 4,054,118; 4,061,124; 4,064,862 and 4,078,538.
The draw length or the length at which the arrow string is pulled to impart potential energy in the limbs of the bow is one of the principal variables of the compound bow and is determined by the physical requirements of the archer. Specifically, an archer of shorter height might prefer a draw length of 26 inches as compared to a taller archer who would prefer a draw length of 30 inches. However, in both cases each archer would desire the same percentage drop-off from the maximum draw weight exerted on the bow during the draw cycle to the weight exerted on the bow in the full draw position. Therefore, in order to effect a change in the draw length but maintain the same percentage drop-off it has been required in the past to utilize pulleys having different diameters so as to provide a change in the length of cable reeved about the pulley. By controlling the diameter size of the pulleys it has been possible to provide variations in the draw weight and draw length of the bow. Thus it has been the practice with conventional compound bows to change pulleys on the limbs to provide a preselected pulley diameter for a preselected draw length, requiring that a number of sets of pulleys of different diameters be made available for each bow. This practice substantially reduces the flexibility of a compound bow to be used for both hunting and competitive purposes and by more than one archer of varying physical characteristics.
The above mentioned U.S. Pat. No. 4,061,124 provides limited adjustment in the draw length of the arrow string for a pulley of a given diameter by increasing or decreasing the length of cable reeved about the pulley. This is accomplished by kinking portions of the cable to thereby limit the amount of cable that can be unwound from the pulley when the arrow string is drawn.
While it has been suggested by the prior art devices to effect a change in the draw length and accordingly the draw weight of the bow, the adjustments available are limited and necessitate substantial disassembly and assembly of components of the bow, particularly the pulley and the portion of the cable reeved around the pulley for eccentric pulley settings. Therefore, there is need to provide in a compound bow apparatus for effecting a plurality of adjustments in the draw length and draw weight of a bow without necessitating substantial disassembly and assembly of the bow so that a compound bow may be more effeciently used for both hunting and competitive purposes.